CWI cheat sheet

AWS filler metal classification EXXYZ: E = electrode; first two digits = minimum tensile strength in ksi (E70 = 70,000 psi); third digit = position (1 = all positions, 2 = flat and horizontal); fourth digit = coating and current type.

E6010 is a cellulosic electrode that runs on DC electrode positive only and gives deep penetration; E7018 is low-hydrogen, runs on AC or DC, and must be held dry (typically 250-300 F holding oven).

Heat input (J/in) = 60 x volts x amps / travel speed (in/min). Increasing heat input slows the cooling rate and lowers hardness, but increases distortion and shrinks the HAZ toughness.

Carbon equivalent: CE = C + Mn/6 + (Cr + Mo + V)/5 + (Ni + Cu)/15. Steels with CE above roughly 0.40 generally require preheat and hydrogen control to avoid delayed cracking.

GMAW transfer modes: short-circuiting for thin sheet and out-of-position work; globular is unstable and avoided; spray requires high current plus argon-rich shielding and is limited to flat and horizontal positions.

GTAW uses a non-consumable tungsten electrode with separately added filler. DCEN concentrates heat for deep penetration in steel; AC is used on aluminum because the electrode-positive half-cycle breaks up the oxide film.

SAW blankets a continuously fed wire under granular flux, giving high deposition and deep penetration; it is normally restricted to flat and horizontal positions because the flux must support the arc.

Fillet weld throat = 0.707 x leg for an equal-leg 45 degree fillet; effective throat, not leg or face width, governs the strength of the weld.

Distortion control methods include balanced (backstep) welding, presetting the parts, restricting heat input, welding from the center outward, and using fixtures or strongbacks.

Inspection takes place in three stages: before welding (materials, fit-up, WPS, welder qualification), during welding (root pass, interpass cleaning), and after welding (final visual, then NDE).

AWS D1.1 requires a minimum illumination of 1000 lux (about 100 foot-candles) on the surface being examined, along with adequate access and line of sight for the inspector.

A discontinuity is any interruption in the material; it becomes a defect only when it exceeds the acceptance criteria of the governing code.

PT detects only surface-breaking discontinuities in nonporous materials. MT detects surface and near-surface discontinuities but works only on ferromagnetic materials (AC for surface sensitivity, DC for deeper flux fields).

UT is strongest on planar reflectors oriented perpendicular to the sound beam; RT is stronger on volumetric flaws but needs access from both sides and cannot reveal laminations parallel to the beam.

Common weld gauges: undercut gauge, V-WAC combination gauge, fillet leg gauge, bridge-cam gauge, taper gauge, and hi-lo gauge for internal misalignment of abutting members.

NDE personnel are qualified to ASNT SNT-TC-1A Level I, II, or III under the employer's written practice; certification is issued by the employer, not by ASNT.

Fillet weld size is measured by leg length, not face width; for an equal-leg 45 degree fillet the theoretical throat is 0.707 times the leg.

Visual discontinuities to identify: undercut, overlap, surface porosity, spatter, arc strikes, crater cracks, incomplete fusion or penetration, and joint misalignment.

AWS code family: D1.1 structural steel, D1.2 aluminum, D1.3 sheet steel, D1.5 steel bridges, D1.6 stainless steel, D9 aluminum structures.

A WPS is prequalified under D1.1 Clause 3 only when the joint detail and every essential variable fall inside the prequalified limits; otherwise the procedure must be qualified by test under Clause 4.

Essential variables include welding process, position, thickness range, filler metal classification, preheat, and current type; changing any one of them requires requalification of the WPS.

D1.1 acceptance limits: butt weld reinforcement shall not exceed 1/8 in (3 mm); undercut shall not exceed 1/32 in (1 mm) except for limited cumulative lengths where 1/16 in is permitted.

Minimum fillet weld size based on thickness of the thinner part: up to 1/4 in = 1/8 in; over 1/4 to 1/2 in = 3/16 in; over 1/2 to 3/4 in = 1/4 in; over 3/4 in = 5/16 in.

A fillet weld must be at least four times its nominal size in length; if shorter, the effective size is taken as the length divided by four.

ASME Section IX qualifies procedures and personnel for pressure equipment through the WPS, the PQR, and welder performance qualification; it is not a construction code.

API 1104 governs the welding of transmission pipelines and related facilities, including girth weld qualification and acceptance criteria.

The inspector's authority derives from the contract documents and the referenced code; every rejection or acceptance should cite the specific code clause or drawing requirement.